Glycols alkaline earth metal complexes

Because the oxygen of ether compounds carries a net negative charge,68 a complex was reported to be formed between the oxygen of compounds such as poly(ethylene glycol) and metal ions, especially alkali metal and alkaline earth metal cations, due to the ion-dipole interactions of the positive charge of the... 

A number of catalysts for the formose reaction are known (see Table I). They are mostly inorganic and organic bases. In particular, the hydroxides of alkaline-earth metals (for example, calcium hydroxide) are most effective, because of their particular ability to form stable complexes with enediol compounds (see formula 1). The reaction occurs not only in aqueous solution but also in anhydrous ethyl alcohol, glycerol, and glycol, or in solutions of organic acids, although less actively. 

A number of reports [10, 17, 22, 25-27] suggest that, in the case of condensation between aromatic diols and polyethylene glycols, the nature of the template exerts an influence on the rate of macrocyclisation. The templates form various series depending on the size of the synthesised crown ether, but lithium ion is an inhibitor in all cases. This must be attributed to the fact that Li+ forms the most stable ion pair with phenolate and simultaneously gives the least stable complexes with benzo crown ethers. It should be noted that alkaline earth metal ions, even in small concentrations, promote these reaction more effectively than alkali metal ions. In addition, it has been emphasised [12] that there is a definite correlation between the basicity of the substance used in the template synthesis of macrocyclic polyethers and the yield of final product. 

Although non-ionic surfactants would appear to be unlikely candidates as complexing agents for metal ions, the interaction of some polyoxyethylene glycols with metal ions has recently attracted interest [90,91]. The reaction of non-cyclic polyoxyethylene derivatives with alkali and alkaline earth metals has been studied by means of solvent extraction of their thiocyanates or iodides. Polyoxyethylene dodecyl ethers with more than 7 ethylene oxide units were able to bind potassium ion in the water phase and to transfer the complexed salt to the organic phase the extracting power of Ci2Eg was about one sixth of that of a crown ether [92]. Some results are shown in Fig. 11.13. 

---